Screwdown control for metal rolling mills



March 18, 1969 G. E. LEMON 3,433,037

SCREWDOWN CONTROL FOR METAL ROLLING MILLS Filed Nov. 7, 1966 9 (n I m m 00 m 2 u) (\l a; Z LI.

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ATTOR NEY United States Patent 3,433,037 SCREWDOWN CONTROL FOR METAL ROLLING MILLS George Edward Lemon, 286 Lora Ave., Youngstown, Ohio 44504 Filed Nov. 7, 1966, Ser. No. 592,392 U.S. C]. 72-35 Int. Cl. B21b 31/34, 13/08, 31/24 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the control of roughing and finishing mill stands of strip rolling mills and more particularly to the control of the spacing of the work rolls of the roll stands.

In the manufacture of steel strip, the incoming slabs or bars from a blooming mill, for example, are run through a series of roughing mill stands to efiect an initial reduction of thickness, and thereafter run through a series of finishing mill stands to effect a further reduction of thickness and to produce a strip of uniform, precisely controlled thickness. The amount of reduction effected by each stand of the rolling mill is determined by the separation of the upper and lower work rolls of each stand, which separation is controlled by screwdowns which raise and lower the upper roll carriers. These screwdowns must be capable of being rapidly and accurately adjusted, both to facilitate initial adjustments and to readily compensate for any unevenness or irregularity of the gauge of the strip during the rolling operation.

In presently employed systems, the indicators provided to indicate the exit gauge or work roll separation of each rolling mill stand read in decimal fractions, one revolution being equivalent to 0.01 inch. When it is desired to roll a gauge different from the one previously rolled, each stand must be readjusted to a different work roll separation, which is difi'icult for the ordinary mill operator to determined. The mill operator must remember the necessary indicator readings and refer to tables giving the change in setting to provide the desired reduction at the particular station, since the changes in settings are different for different stations. This is both time-consuming and subject to errors on the part of the operator.

It is the primary object of this invention to provide means for adjusting the gauge of all the roll stands of a strip rolling mill by the same amount, that is by a single screwdown turn, whereby all the roll stands may be adjusted with one control and whereby the openings or separation between rolls in the last six stations are in the ratio of 1.5, 1.5, 1.5, 1.3, 1.10 and 1.0, respectively, which is accomplished by appropriately designed shaft threads or gears.

A further object of the invention is the provision of screwdown indicators and control means whereby the rolling stands of a strip rolling mill may be readily adjusted to compensate for any unevenness or irregularity in the bar or slab being rolled.

Another object of this invention is the provision of screwdown indicator and control means which are simple and inexpensive to construct and which provide troublefree operation under a wide variety of operating condiice tions without involving the necessity of costly automatic equipment but which substantially improve the operating efliciency of the mills. For a complete understanding of the principles and advantages of my invention reference should first be had to the appended drawing which illustrates more or less schematically the preferred embodiment of the invention.

In the drawing:

FIGURE 1 is a schematic showing of a rolling mill installation with which my invention may be utilized; and

FIGURES 2A and 2B are graphs showing the screwdown drive ratios of the roughing and finishing stands, respectively, of FIGURE 1.

In FIGURE 1 reference numeral 10 designates a typical stand of a strip rolling mill. The stand 10 consists of a housing 11, lower roll carrier 12, upper roll carrier 13, lower pressure roll 14, lower work roll 15, upper pressure roll 16, upper work roll 17, and screw 18 which is threaded in the upper portion 10' of housing 10. The lower end of screw 18 is secured to upper roll carrier 13. It will be understood that there is a screw provided for the upper roll carrier in which the far ends of the upper pressure and work rolls are journaled. A gear 19 is secured against rotation to the upper end of screw 18 and is driven by a suitable motor (not shown) through worm gear 20. With each mill stand 10 there is provided an indicator 21 having hands 22 and 23 to indicate the position of the near and far ends, respectively, of upper work roll 17 with respect to the corresponding ends of lower work roll 15. As is well known in the art suitable circuitry is provided to operate the motors which drive worm 20 and thus raise and lower work rolls 17. Although only four stands are shown in the drawing, a typical strip rolling mill installation may consist of four roughing mill stands and six finishing mill stands.

In my invention, screws 18 have differing pitches depending upon the location of the stand in the rolling mill; thus, as is shown in FIGURES 2A and 2B, the pitch of the screws of the first roughing stand S1 is greater than that of the screws of the next roughing stand and of the screws of each succeeding stand of the mill. In the same manner, each succeeding stand has screws whose ptich is greater than that of the screws of following stands but less than that of the screws of preceding stands.

I have found that if the screws of stands S1, S2, S3 and S4, the roughing stands of the mill, effect reductions of 0.4, 0.3, 0.2, and 0.1 inch per revolution, respectively, and the screws of stands S5 through S10, the finishing stands of the mill, effect reductions of 0.015, 0.015, 0.015, 0.013, 0.011, and 0.010 inch per revolution, respectively, the screws of each roll stand will bring the work rolls of their stands into the necessary position for the rolling of a specified gauge from the initial position of the rolls in the same number of turns of each screw. In short, for optimum rolling conditions, the last six rolls, namely, the finishing rolls, should have separations or openings having ratios, compared to the exit gauge of 1.5, 1.5, 1.5, 1.3, 1.1, and 1.0, respectively. Minor variations may be made however depending on sheet thickness, for example. The indicators 21 utilized in my invention indicate the number of revolutions of the screw 18; one revolution of the screw 18 being equivalent to one revolution of hand 22. In addition to the dial indicator 21 I provide a counter 24 associated therewith which indicates the number of revolutions of hand 22. The counter 24 is so designed as to be resettable to zero When desired. It is unnecessary to provide an additional counter for hand 23 since during all major adjustments hands 22 and 23 rotate together and when making adjustments to compensate for irregularities of the strip being rolled it is seldom necessary to rotate either screw more than a fraction of one revolution.

When the strip rolling mill utilizing my invention is to be adjusted to produce, for example, a gauge or thickness of 0.100 inch from material of a thickness of 4.5 inches, the roughing mill stands S1 through S4 are set at 7, 7, 7, 10 revolutions, respectively, and the finishing mill stands S5 through S are set at ten revolutions each. Similar figures apply for the rolling of different gauge material and it is clearly evident that this method is far easier for the strip mill operator to remember and use than is the presently employed system.

On the existing equipment where it would be difficult and costly to replace the screws, the abovementioned ratios may be achieved by using suitable combinations of the gears 19 and 20.

From the above it is clearly evident that I have invented a new and useful control for determining and regulating the work roll separation of strip rolling mills which is economical to construct and which reduces the possibility of erroneous settings of the roll position. Furthermore, I have invented an optimum sequence of separation between upper and lower work rolls, particularly, in the finishing rolls, so as to obtain an optimum finish, also so that the same adjustment, namely one turn of a screw, may be used on each of the finishing stands in order to simplify the task of the operator and eliminate or minimize errors in adjustment. It is further evident that the system of my invention is readily adapted to existing strip rolling mill equipment.

Having described my invention what I claim is:

1. In multi-stand strip rolling equipment for producing elongated metal strip from bars or slabs wherein there are provided upper and lower work rolls to effect reduction in thickness of the material being rolled and wherein the position of the upper work rolls is adjustable with respect to the lower work rolls by means of screws, the improvement comprising: screws having differing pitches dependent upon with which of the stands said screws are associated, whereby said upper work rolls may be moved ditfering amounts in differing ones of said stands by the same amount of rotation of said screws; and indicators to indicate the position of said upper work rolls with respect to said lower work rolls.

2. Apparatus according to claim 1 further characterized in that said multi-stand rolling mill is composed of four roughing stands and six finishing stands, the screws of said roughing stands etfecting movement of said upper work rolls of 0.4, 0.3, 0.2, and 0.1 inch, respectively, per revolution, and the screws of said finishing stands effecting movement of said work rolls of their respective stands of 0.015, 0.015, 0.015, 0.013, 0.011, and 0.010 inch per revolution.

3. Apparatus according to claim 1 further characterized in that said indicators are provided with two indicating hands to indicate the positions of the two screws of each stand, said indicator hands making one revolution for each revolution of said screws, and counter means to indicate the number of revolutions made by one of said hands.

4. Apparatus according to claim 1 further characterized in that said multi-stand rolling mill includes six finishing stands whose successive separations between upper and lower work rolls are in the ratio, to the exit gauge, of approximately 1.5, l.5, 1.5, 1.3, 1.1, and 1.0, in succession, to obtain optimum successive reductions for the finishing operation.

5. Apparatus according to claim 4 further characterized in that each of said successive, different separations is effected by a single turn of an adjusting screw at each stand.

References Cited UNITED STATES PATENTS 2,949,799 8/1960 Walker 72--234 2,959,992 11/1960 Mitchell 72-234 CHARLES W. LANHAM, Primary Examiner.

B. J. MUSTAIKIS, Assistant Examiner.

US. Cl. X.R. 

